Add runtime telemetry coverage metadata

[hyeokjun32]

Summary

• add runtime_telemetry.coverage metadata for expected, observed, and missing telemetry fields
• keep EdgeEnv as comparability owner and missing telemetry as an evidence gap, not a failure
• extend smoke and schema tests for telemetry coverage counts and runtime event summary fields

Tests

• bash scripts/smoke_default.sh
• python3 tests/test_lab_result_schema.py && python3 tests/test_agent_runtime_result_contract.py && python3 tests/test_manifest_compare_identity.py
• python3 -m unittest discover -s tests -p 'test_*.py'

Note: direct Python tests were run outside the sandbox because the Runtime binary updates results/latest.json.